Morphometric Comparison and Prognostic Analysis of Permanent Maxillary Central Incisors with Eruption Disturbances-A Cross-Sectional Study.

AIMS: The aim of this study was to retrospectively compare the morphometrics of permanent maxillary central incisors with and without eruption disturbances, while simultaneously evaluating prognosis based on different factors. MATERIALS AND METHODS: Seventy patients with unilateral permanent maxillary central incisor eruption disturbances were included. Within a group of 70 subjects, measurements were taken for both normally erupted central incisors and central incisors with eruption disturbances to determine the length of the roots and the volume of the teeth. Various factors, such as angulation of impaction, and vertical height of impaction, were assessed to investigate their correlation with surgical intervention. RESULTS: Both the root length and tooth volume were significantly smaller in the eruption disturbance incisors than in the normally erupted incisors (p ≤ 0.001). Moreover, there was a statistically significant increase in surgical intervention among cases with no clear physical barrier (primary retention) (p < 0.05) or when adjacent normally erupted central incisors exhibited more than 2/3 of root development (p < 0.05). CONCLUSIONS: The results of this study numerically demonstrated the delayed tooth development of the permanent maxillary central incisors with unilateral eruption disturbances compared to appropriately erupted incisors by measuring root length and tooth volume. The absence of obstacles and the degree of root development in adjacent erupted incisors might serve as factors for clinicians to determine the necessity and timing of surgical intervention.

Strength and Surface Characteristics of 3D-Printed Resin Crowns for the Primary Molars.

Some resin polymers available for three-dimensional (3D) printing are slightly elastic, which may be advantageous when used for full crown coverage of the primary teeth. This study was performed to evaluate the mechanical properties of two types of 3D-printed resin crowns in terms of strength and surface characteristics. Polymer resins used for temporary crowns (TCs) and temporary flexible dentures (TFDs) were tested. Digitally designed crowns with different thicknesses (0.4 and 0.6 mm) were 3D-printed. Milled zirconia crowns were used as the control. The static and dynamic fracture loads of the crowns were measured. The crown surface was evaluated using scanning electron microscopy. The average strength did not differ between the types of crowns. The differences between the dynamic and static fracture loads were insignificant. In the TC group, thicker crowns showed lower strength both under static and dynamic loads. After thermomechanical loading, microcracks and dropouts of macrofillers were detected on the surface of all types of resin crowns. The deposition of abraded debris occurred more in the TFD group. The 3D-printed resin crowns were thought to endure biting forces in children. However, some limitations of the material itself should be improved for consideration as a new treatment option in pediatric dentistry.

Guided Autotransplantation of Impacted Canines Using a CAD/CAM Surgical Template.

Autotransplantation is a potential treatment alternative when orthodontic traction of an impacted tooth is difficult. In this article, we describe two cases of guided autotransplantation of an impacted canine using a computer-aided designed and manufactured surgical template. The impacted canine was segmented on preoperative cone-beam computed tomography images to ensure a sufficient periodontal ligament space and placement of the donor tooth with the least pressure on it. The canine was virtually transposed using a simulation program considering the adjacent teeth. The surgical template, which was connected to the occlusal stop on adjacent teeth, was designed and 3D-printed with polymer resin. The recipient site was prepared using the surgical template, followed by immediate transplantation of the surgically extracted canine into the socket. The transplanted donor tooth was positioned in planned infra-occlusion to prevent occlusal interference. It was then splinted with the adjacent teeth for initial stabilization. During follow-up, one transplanted tooth showed pulp canal obliteration and the other had suspected pulp necrosis; endodontic treatment was performed. One year after the procedure, the periradicular condition of both teeth was favorable.

Deep learning-based identification of mesiodens using automatic maxillary anterior region estimation in panoramic radiography of children.

OBJECTIVES: The purpose of this study is to develop and evaluate the performance of a model that automatically sets a region of interest (ROI) and diagnoses mesiodens in panoramic radiographs of growing children using deep learning technology. METHODS: Out of 988 panoramic radiographs, 489 patients with mesiodens were classified as an experimental group, and 499 patients without mesiodens were classified as a control group. This study consists of two networks. The first network (DeeplabV3plus) is a segmentation model that uses the posterior molar space to set the ROI in the maxillary anterior region with the mesiodens in the panoramic radiograph. The second network (Inception-resnet-v2) is a classification model that uses cropped maxillary anterior teeth to determine the presence of mesiodens. The data were divided into five groups and cross-validated. Deep learning model were created and trained using Inception-ResNet-v2. The performance of the segmentation network was evaluated using accuracy, Intersection over Union (IoU), and MeanBFscore. The overall network performance was evaluated using accuracy, precision, recall, and F1-score. RESULTS: Segmentation performance using posterior molar space in panoramic radiographs was 0.839, IoU 0.762, and MeanBFscore 0.907. The mean values of accuracy, precision, recall, F1-score, and area under the curve for the diagnosis of mesiodens using automatic segmentation were 0.971, 0.971, 0.971, 0.971, and 0.971, respectively. CONCLUSIONS: The diagnostic performance of the deep learning system using posterior molar space on the panoramic radiograph was sufficiently useful. The results of the deep learning system confirmed the possibility of complete automation of the classification of mesiodens.

Microbiome of Saliva and Plaque in Children According to Age and Dental Caries Experience.

Dental caries are one of the chronic diseases caused by organic acids made from oral microbes. However, there was a lack of knowledge about the oral microbiome of Korean children. The aim of this study was to analyze the metagenome data of the oral microbiome obtained from Korean children and to discover bacteria highly related to dental caries with machine learning models. Saliva and plaque samples from 120 Korean children aged below 12 years were collected. Bacterial composition was identified using Illumina HiSeq sequencing based on the V3-V4 hypervariable region of the 16S rRNA gene. Ten major genera accounted for approximately 70% of the samples on average, including Streptococcus, Neisseria, Corynebacterium, and Fusobacterium. Differential abundant analyses revealed that Scardovia wiggsiae and Leptotrichia wadei were enriched in the caries samples, while Neisseria oralis was abundant in the non-caries samples of children aged below 6 years. The caries and non-caries samples of children aged 6-12 years were enriched in Streptococcus mutans and Corynebacterium durum, respectively. The machine learning models based on these differentially enriched taxa showed accuracies of up to 83%. These results confirmed significant alterations in the oral microbiome according to dental caries and age, and these differences can be used as diagnostic biomarkers.

Automated Mesiodens Classification System Using Deep Learning on Panoramic Radiographs of Children.

In this study, we aimed to develop and evaluate the performance of deep-learning models that automatically classify mesiodens in primary or mixed dentition panoramic radiographs. Panoramic radiographs of 550 patients with mesiodens and 550 patients without mesiodens were used. Primary or mixed dentition patients were included. SqueezeNet, ResNet-18, ResNet-101, and Inception-ResNet-V2 were each used to create deep-learning models. The accuracy, precision, recall, and F1 score of ResNet-101 and Inception-ResNet-V2 were higher than 90%. SqueezeNet exhibited relatively inferior results. In addition, we attempted to visualize the models using a class activation map. In images with mesiodens, the deep-learning models focused on the actual locations of the mesiodens in many cases. Deep-learning technologies may help clinicians with insufficient clinical experience in more accurate and faster diagnosis.

Comparison of Deep Learning Models for Cervical Vertebral Maturation Stage Classification on Lateral Cephalometric Radiographs.

The purpose of this study is to evaluate and compare the performance of six state-of-the-art convolutional neural network (CNN)-based deep learning models for cervical vertebral maturation (CVM) on lateral cephalometric radiographs, and implement visualization of CVM classification for each model using gradient-weighted class activation map (Grad-CAM) technology. A total of 600 lateral cephalometric radiographs obtained from patients aged 6-19 years between 2013 and 2020 in Pusan National University Dental Hospital were used in this study. ResNet-18, MobileNet-v2, ResNet-50, ResNet-101, Inception-v3, and Inception-ResNet-v2 were tested to determine the optimal pre-trained network architecture. Multi-class classification metrics, accuracy, recall, precision, F1-score, and area under the curve (AUC) values from the receiver operating characteristic (ROC) curve were used to evaluate the performance of the models. All deep learning models demonstrated more than 90% accuracy, with Inception-ResNet-v2 performing the best, relatively. In addition, visualizing each deep learning model using Grad-CAM led to a primary focus on the cervical vertebrae and surrounding structures. The use of these deep learning models in clinical practice will facilitate dental practitioners in making accurate diagnoses and treatment plans.

Positional Differences of the Mandibular Canal in Relation to Permanent Mandibular First Molars with Eruption Disturbances in Children.

Eruption disturbances in permanent mandibular first molars (PM1s) are uncommon. This retrospective study aimed to investigate differences in the position of the mandibular canal in relation to PM1s, with or without, eruption disturbances. Panoramic and cross-sectional views were reconstructed from cone-beam computed tomography imaging of children with PM1 eruption disturbances. Distances from the most inferior margin of the mandible to the center of the mandibular canal (M-C) and from the outer margin of the lingual cortex to the center of the mandibular canal (L-C) were measured for normally erupted PM1s (normal group) and for PM1s with eruption disturbances (ED group) and compared using independent t-tests. The mean M-C was significantly shorter in the ED group (4.86 ± 1.07 mm) than in the normal group (6.56 ± 1.06 mm) (p < 0.05). The mean L-C was also significantly shorter in the ED group (2.74 ± 0.74 mm) than in the normal group (3.09 ± 0.71 mm) (p < 0.05). This study demonstrated that the mandibular canal tended to be positioned more inferiorly in relation to PM1s with eruption disturbances than normally erupted PM1s in children. Clinicians should be aware of this positional deviation when managing children with PM1 eruption disturbances.

Oncostatin M enhances osteogenic differentiation of dental pulp stem cells derived from supernumerary teeth.

Supernumerary tooth (ST) may arise from uncertain developmental abnormalities or underlying genetic causes, and the extraction at the early age is recommended. Dental pulp stem cells (DPSCs) are the valuable resource for the regeneration of tooth and related craniofacial structures. DPSCs isolated from ST (sDPSCs) have not been fully characterized despite the potential in the applications. The objectives of this study are the efficient isolation of sDPSCs and the analysis of the properties as stem cells. sDPSCs were established by hammer-cracking and separation of the intact pulp from ST. sDPSCs in the culture were examined by light microscope and flow cytometer for the morphology and the surface marker expression. sDPSCs exhibited the cellular morphology of typical mesenchymal stem cells and expressed CD44, CD73, CD90, CD105 and CD166, but not CD14, CD34 or CD45. sDPSCs showed the differentiation potential toward osteogenic, chondrogenic and adipogenic lineages. During osteogenic differentiation, the stimulation by Oncostatin M enhanced the differentiation and significantly increased the expression of genes involved in the hard tissue repair, such as BMP2, BMP4, BMP6 and RUNX2. sDPSCs can be effectively derived from ST and displays the characteristics of mesenchymal stem cells in the maintenance and the differentiation. sDPSCs satisfies the quality as DPSCs thus provide the valuable resource to the regenerative therapy.

Ameloblastic Fibro-Odontoma Misidentified as an Enamel Pearl.

Ameloblastic fibro-odontoma (AFO) is a rare, benign, and mixed odontogenic tumor that consists of both ectodermal and mesenchymal elements. AFO is more prevalent in young children and adolescents than in adults and is usually found in the molar area associated with a failure of tooth eruption. The purpose of this report is to discuss the differential diagnosis and treatment of a three-year-old girl diagnosed with an AFO around a primary canine. The manifestations of the lesion resembled localized periodontal disease caused by an enamel pearl. Excision and curettage were done and the separated dental hard tissue was confirmed from the enamel structure of the primary canine. In addition to the hard tissue, pulpy and soft tissues were removed together and were histologically examined, confirming the diagnosis of AFO.

Difference assessment of composite resins and sound tooth applicable in the resin-imbedded tooth for resin repair using fluorescence, microhardness, DIAGNOdent, and X-ray image.

OBJECTIVE: Visual differentiation of resin and tooth in a tooth cavity is not simple due to their highly similar shade. The purpose of the present study was to find any noninvasive method which can effectively differentiate resin from sound tooth in a resin-imbedded tooth for resin repair. MATERIALS AND METHODS: For the study, various resin products were imbedded into the cavity of sound tooth. By applying laser of different wavelengths, autofluorescence (AF) of sound tooth and resin products were obtained. Microhardness, X-ray radiograph, and DIAGNOdent were tested for each tooth, resin product, and resin-imbedded tooth. RESULTS: For the AF spectra obtained using the 405-nm wavelength, sound tooth has emission peak at 440-470 nm and near 490 nm. Sound tooth has several times higher microhardness than resin products regardless of position in tooth subsurface. Due to the difference of radiopaque fillers' composition and concentration, resin products have different brightness in the X-ray radiograph. DIAGNOdent readings for tooth and resin products were inconsistently different, and the difference of obtained values was slightly not to be applicable for the differentiation. CONCLUSION: Among the tested methods, with noninvasive treatment, AF spectrum by the 405-nm wavelength showed the apparent difference between resin and tooth. CLINICAL SIGNIFICANCE: For the resin repair in a resin-imbedded tooth cavity, AF spectrum produced by 405-nm wavelength could be a useful method in tracing the resin-tooth boundary if combined with conventional X-ray radiography.

Effects of mesiodens on adjacent permanent teeth: a retrospective study in Korean children based on cone-beam computed tomography.

BACKGROUND: Mesiodens can be associated with several complications. The optimal age for treatment, however, remains controversial. AIM: To investigate the three-dimensional (3D) positions of mesiodens using cone-beam computed tomography (CBCT) and determine the association of eruption-related complications of mesiodens with these 3D positions and delayed development of the central incisors. DESIGN: In total, 293 Korean children (383 supernumerary teeth) aged 4-10 years with no history of orthodontic treatment were included. CBCT and panoramic radiography data for all patients were retrospectively investigated with regard to the 3D positions of mesiodens, apical maturity of the permanent first molars, delayed development of the central incisors relative to the apical maturity of the permanent first molars (Nolla's stage), and eruption-related complications of mesiodens. RESULTS: Eruption-related complications were not correlated with any 3D characteristic other than the 'within the arch' position of mesiodens, while they showed a significant correlation with delayed development of the central incisors (P < 0.05). CONCLUSIONS: Mesiodens caused eruption-related complications in 33.7% patients. Moreover, the risk of these complications was higher when mesiodens caused delayed development of the central incisors. These findings can aid clinicians in planning appropriate and timely treatment for mesiodens, with focus on minimising patient discomfort.

In Vitro Investigation of Wear of CAD/CAM Polymeric Materials Against Primary Teeth.

The aim of the study was to evaluate the effects of polymeric computer-aided design/computer-aided manufacturing CAD/CAM materials on antagonistic primary tooth wear. Five CAD/CAM polymeric materials were examined: Vipi Block Monocolor (VBM), Yamahachi polymethylmethacrylate (PMMA) (YAP), Mazic Duro (MZD), Vita Enamic (ENA), and Pekkton (PEK). All of the specimens were tested in a thermomechanical loading machine with the primary canine as the antagonist (50 N, 1.2 × 105 cycles, 1.7 Hz, 5/55 °C). The wear losses of the antagonist tooth and the restorative materials were calculated using reverse modelling software and an electronic scale. VBM and ENA showed significantly higher antagonist tooth wear than PEK (p < 0.05), but there was no significant difference observed among VBM, YAP, MZD, and ENA (p > 0.05). PEK showed the largest value in both material volumetric and weight losses. In terms of material volumetric losses, there was no significant difference between all of the groups (p > 0.05). In terms of material weight losses, PEK was significantly larger than ENA (p < 0.05), but there was no significant difference between VBM, YAP, MZD, and ENA (p > 0.05). Volumetric and weight losses of materials showed similar wear behaviour. However, the wear patterns of antagonists and materials were different, especially in PEK.

Development of a Web-Based Nationwide Korean Pediatric Dental Sedation Registry.

OBJECTIVE: Finding a balance between sedation efficacy and safety remains an ongoing challenge. In children, the risk of sedation-related complications is relatively high. It is of utmost importance to determine the factors related to improved overall sedation outcomes. However, most previous reports have been based on small samples at single institutions. The Korean Academy of Pediatric Dentistry (KAPD) developed a Korean Pediatric Dental Sedation Registry using a web-based platform. STUDY DESIGN: Specialists in pediatric dental sedation selected the itemized list included within the registry through an extensive literature review. The web-based registry was built into the KAPD homepage to facilitate easy access to the sedation data. All teaching and university hospitals agreed to participate in the Korean Pediatric Dental Sedation Registry. CONCLUSION: This is the first attempt to collect sedation data on a nationwide scale in the field of pediatric dentistry. The sedation database established with the registry may facilitate standardizing and improving pediatric dental sedation clinical practices.

Effects of Additional Acid Etching on the Dentin Bond Strengths of One-Step Self-Etch Adhesives Applied to Primary Teeth.

OBJECTIVES: The aim of this study was to evaluate the bond strengths of one-step self-etch adhesives applied to primary tooth dentin with and without additional acid etching. MATERIALS AND METHODS: In total, 154 specimens were prepared using 50 naturally exfoliated primary molars. Four commercial one-step self-etch adhesives were used in this study: Scotchbond™ Universal, All-Bond Universal™, Adper™ Prompt™ L-Pop™, and Clearfil S3 Bond™. Two etch-and-rinse adhesives, Prime & Bond® NT™ and Scotchbond™ Multi-Purpose, served as controls. Microtensile bond strength tests were performed for specimens treated with the one-step self-etch adhesives with and without additional acid etching and those treated with the two etch-and-rinse adhesives. RESULTS: All one-step self-etch adhesives except Adper Prompt L-Pop exhibited increased microtensile bond strength values (p < 0.05) with additional acid etching. A nonsignificant interaction was observed between the type of self-etch adhesive and additional acid etching (p = 0.056). Bond strength comparisons between the self-etch adhesives used without additional acid etching and the etch-and-rinse adhesives revealed significantly higher values for Prime & Bond NT than for All-Bond Universal® (p < 0.05). However, there were no significant differences between any etch-and-rinse adhesive and self-etch adhesive used with additional acid etching, although Clearfil S3 Bond showed greater strength than Adper Prompt L-Pop. CONCLUSIONS: Our results suggest that additional acid etching increases the bond strength of most one-step self-etch adhesives applied to primary tooth dentin. CLINICAL SIGNIFICANCE: Additional acid etching of enamel and dentin can be recommended to increase the bond strength of one-step self-etch adhesives applied to primary teeth. (J Esthet Restor Dent 29:110-117, 2017).

Wear of primary teeth caused by opposed all-ceramic or stainless steel crowns.

PURPOSE: This study was conducted to evaluate the effects of full-coverage all-ceramic zirconia, lithium disilicate glass-ceramic, leucite glass-ceramic, or stainless steel crowns on antagonistic primary tooth wear. MATERIALS AND METHODS: There were four study groups: the stainless steel (Steel) group, the leucite glass-ceramic (Leucite) group, the lithium disilicate glass-ceramic (Lithium) group, and the monolithic zirconia (Zirconia) group. Ten flat crown specimens were prepared per group; opposing teeth were prepared using primary canines. A wear test was conducted over 100,000 chewing cycles using a dual-axis chewing simulator and a 50 N masticating force, and wear losses of antagonistic teeth and restorative materials were calculated using a three-dimensional profiling system and an electronic scale, respectively. Statistical significance was determined using One-way ANOVA and Tukey's test (P<.05). RESULTS: The Leucite group (2.670±1.471 mm(3)) showed the greatest amount of antagonist tooth wear, followed by in decreasing order by the Lithium (2.042±0.696 mm(3)), Zirconia (1.426±0.477 mm(3)), and Steel groups (0.397±0.192 mm(3)). Mean volume losses in the Leucite and Lithium groups were significantly greater than in the Steel group (P<.05). No significant difference was observed between mean volume losses in the Zirconia and Steel groups (P>.05). CONCLUSION: Leucite glass-ceramic and lithium disilicate glass-ceramic cause more primary tooth wear than stainless steel or zirconia.

Effect of dual-peak LED unit on the polymerization of coinitiator-containing composite resins.

The purpose of the present study was to evaluate the effect of dual-peak LED on the polymerization of coinitiator-containing composite resins. For this, microhardness, degree of conversion (DC), and polymerization shrinkage were evaluated. Specimens (coinitiator-containing: Aelite LS Posterior, Tetric EvoCeram, and Vit-l-escence; only camphorquinone-containng: Filtek Z350 and Grandio) were light cured using a quartz-tungsten-halogen (QTH: OP), a single-peak light-emitting diode (LED) (L. E. Demetron: DM), and a dual-peak LED (G-light: GL), respectively. All specimens light cured using GL showed the highest microhardness both on the top and bottom surfaces compared with the values obtained using the rest light-curing units (LCUs). DC had no consistent trend correspond to the LCU, but rather product specific. OP yielded the lowest polymerization shrinkage on the specimens. The coinitiator-containing composite resins achieved the highest microhardness by the dual-peak LED (GL). However, the influence of GL on DC and polymerization shrinkage of the specimens was not consistent.

The evaluation of resin infiltration for masking labial enamel white spot lesions.

OBJECTIVE: The aim of this study was to clinically assess the effectiveness of masking white spot enamel lesions using a resin infiltration technique that was recently developed to arrest incipient caries in a micro-invasive concept. METHODS: Twenty teeth with a Developmental Defect of Enamel (DDE) and 18 teeth with Post-orthodontic Decalcification (POD) were selected and treated with resin infiltration. Standardized photographs were taken before, immediately after, and 1 week after treatment and were analysed using image analysing software to calculate the ΔE values. The results were classified into three groups: completely masked, partially masked, and unchanged. RESULTS: Among the 20 teeth with DDE, five teeth (25%) were classified as completely masked, whereas seven (35%) and eight teeth (40%) were partially masked and unchanged, respectively. Among the 18 teeth with POD, 11 teeth (61%) were completely masked, six teeth (33%) were partially masked, and one tooth (6%) was unchanged. In some teeth, the result was more improved after 1 week than immediately after infiltration. CONCLUSION: The masking effect was dramatic in some cases but not in others. The long-term colour stability of the result should be followed up through continuous clinical and scientific studies.

The effect of resin shades on microhardness, polymerization shrinkage, and color change of dental composite resins.

The present study sought to evaluate the effect of resin shades on the degree of the polymerization. To this end, response variables affected by the degree of polymerization were examined in this study - namely, microhardness, polymerization shrinkage, and color change. Two commercial composite resins of four different shades were employed in this study: shades A3, A3.5, B3, and C3 of Z250 (Z2) and shades A3, A3.5, B3, and B4 of Solitaire 2 (S2). After light curing, the reflectance/absorbance, microhardness, polymerization shrinkage, and color change of the specimens were measured. On reflectance and absorbance, Z2 and S2 showed similar distribution curves regardless of the resin shade, with shade A3.5 of Z2 and shade A3 of S2 exhibiting the lowest/highest distributions. Similarly for attenuation coefficient and microhardness, the lowest/highest values were exhibited by shade A3.5 of Z2 and shade A3 of S2. On polymerization shrinkage, no statistically significant differences were observed among the different shades of Z2. Similarly for color change, Z2 specimens exhibited only a slight (DeltaE*=0.5-0.9) color change after immersion in distilled water for 10 days, except for shades A3 and A3.5. Taken together, results of the present study suggested that the degree of polymerization of the tested composite resins was minimally affected by resin shade.

Biosynthesis of rubradirin as an ansamycin antibiotic from Streptomyces achromogenes var. rubradiris NRRL3061.

The four overlapping cosmids from the rubradirin producer, Streptomyces achromogenes var rubradiris NRRL 3061, have 58 ORFs within a 105.6 kb fragment. These ORFs harbored essential genes responsible for the formation and attachment of four distinct moieties, along with the genes associated with regulatory, resistance, and transport functions. The PKS (rubA) and glycosyltransferase (rubG2) genes were disrupted in order to demonstrate a complete elimination of rubradirin production. The rubradirin biosynthetic pathway was proposed based on the putative functions of the gene products, the functional identification of sugar genes, and the mutant strains.